Your every attack (except orcs with range attacks ) bring you cp (paladins get cp for healing, bat for restoration don’t get).
This points equal 0 at battle start. For this points you can cast some skills, such a plague, black ice and e.t.c

With 20 level you get some strong abilities for cp, that can change battle (sky fire, instant freeze, invulnerability, ring of immortality and e.t.c. ).

With 10 level, you get some useful abilities, that may be change your game (such a steam hammer, shield strike, righteous rage ant e.t.c.). At first they won’t be strong, but, if you spend some level points to them – they will be really useful.

Sappers get’s class points for totems and teleports, all their abilities – support at all (so get’s 2 cp, if enemy go through trap).
Paladins gets 2 cp for healing. All they abilities – supports.
Berserks and inqs get cp for striking and killing.
Ice witch gets cp for freezing enemies (or for shooting frost bolts).
Gunner gets cp for shooting from cannon and when tesla pole hurt enemy’s.
sister of fire gets cp for fire bolts.
Tanks gets cp at the combat.

So, you should know that orcs don’t get cp for kerns.
For the shooting from the bow, humans get 1 cp for hit.
Dwarfs – 2 cp for hit from arquebus.
Ice witch gets 2 cp for bolt.
Sister of fire – 3 cp for bolt.